Electrical relay



March 24 1959 HANS-.JOACHIM wlcHMANN 2,879,353

ELECTRICAL RELAY lFiled May lO, 1955 United States Patent y 2,819,353 ELECTRICAL RELAY Hans-Joachim Wichmann, Nurnberg, to Metrawatt, Fabrik Elektrischer berg, Germany Germany, assigner Messgerate, Nurn- This invention concerns an electrical relay having a locking and release mechanism.

It is an object of the invention to provide a relay having self-holding operating contacts for connection in a circuit external to the relay, which relay can be released into an operative condition by means of a very small force, such as is afforded, for example, by an electrical measuring instrument, the operating contacts, however, being capable of carrying a power of several kilowatts.

According to the present invention the relay is provided with a pivotably mounted two-armed lever, which in the position of rest is in unstable equilibrium and is held approximately in this position by a locking device adapted to be released by a very small force and practically not loaded by the two-armed lever in the condition of unstable equilibrium. On release of the locking dcvice, the two-armed lever tilts from the position of unstable equilibrium either in a clockwise direction or in the opposite direction, until it strikes the operating contacts or a further, intermediate release lever. The position of unstable equilibrium of the two-armed lever may result from its centre of gravity being positioned above its pivotal axis. It is more convenient, however, to subject the two ends of this lever to the 4action of magnetic forces of substantially equal strength.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which:

Fig. l is a side elevation of the relay provided with a locking and releasing mechanism constructed in accordance with the invention,

Fig. 2 is a plan view of the relay shown in Fig. 1, and Fig. 3 is a plan view of a further construction of relay. i In Figs. 1 and 2, 1 is a base plate which carries a relay 2 and a locking and releasing mechanism 3.

The locking and release mechanism 3 consists of a moving coil measuring apparatus known per se and having a permanent magnet 4, a moving coil 5 and an indicator 6. 7 and 8 are connections to the moving coil 5, by means of which a current impulse can be supplied to the latter.

The moving coil 5 together with the indicator 6 is held in the rest position shown in Fig. 1, for example, by means of Va spiral spring (not shown) such as is usual in electrical measuring instruments.

The relay 2 has a permanent magnet 9 with two pole pieces and 11. These pole pieces are both forked in construction, that is, the end remote from the permanent magnet 9 has two projecting members. This is seen best from Fig. 2, in which the pole piece 10 is shown partly broken away. The ends 10a and 11a of the two projecting bifurcations of both pole pieces are bent over towards one another, as seen in Fig. 1, so that an air gap 12 is formed.

To the pole pieces 10 and 11 are attached leads 13 and 14 of a circuit which also contains a battery 15 and an electric lamp 16. In order to avoid closing this circuit i2,879,353 Patented Mar. 24, 1959 2 via the magnet 9, the latter is made of an oxide material, which is not electrically conducting.

Facing the pole pieces 10 and 11 is a two-armed lever 17 mounted on a spindle 17c which runs at right angles to the axis of the moving coil 5, and therefore is situated at least approximately in the plane in which the indicator 6 oscillates. The bearings of the spindle 17c are mounted on the base plate 1. At its outer ends, the double-armed lever 17 is provided with small plates 17a and 17b made of ferromagnetic material. In addition, it is provided with a further arm 18 extending perpendicularly to the lever 17. This arm carries an element 19 having two bent vanes 19a and 191), between which is formed a recess 20.

When the lever 17 is opposite the ends of the pole pieces 10 and 11 in the position of unstable equilibrium shown in Fig. 2, in which magnetic forces of substantially equal size act on the small plates 17a and 17b, then the recess 20 lies in the plane of the indicator 6 and the latter is partly engaged in recess 20.

The lever 17 is thus locked in its position of unstable equilibrium according to Fig. 2.

If now an operating current is supplied to the moving coil 5 via the leads 7 and 8, the coil rotates in one or the other direction. In either case, the indicator 6 emerges from the recess 20, whilel the double-armed lever 17, following the magnetic pull, closes with the rightor left-hand ends of the forked pole pieces 10, 11 with one of the small plates 17a or 17b, and thereby bridges the air gap 12. In this way the two pole pieces 10 and 11 are electrically connected with each other, so that the circuit 13, 14, 15, 16 is closed and the lamp 16 lights up. The small plates 17a and 17b and the points of the pole pieces 10 and 11, with which they come in contact, may conveniently be provided with a facing of precious metal to ensure a good contact. In order to restore the relay 2 to the starting position shown in Fig. 2, there is provided a spring-loaded press button 21, actuated against the force exerted by a spring 22. Press button 21 is displaceably mounted in the magnet 9, and carries a fork 23 which can be moved into the air gap 12. By pressing the button 21 inwards, the fork 23 emerges from the air gap 12, during which movement it restores the double-armed lever 17 into the position of unstable equilibrium. Then, after interruption of the supply of current through the leads 7 and 8, the indicator 6 which has returned once more into its starting position according to Fig. 1, slides on the vanes 19a and 19]; into the recess 20. The double-armed lever 17 is then again locked in its position of unstable equilibrium.

Fig. 3 shows another embodiment of the invention, in which the same reference numerals are utilised to indicate the same parts as in Figs. 1 and 2. The permanent magnet 9 used in this case does not consist of nonconducting material.

A pivotal axle 24 attached to the base plate 1 carries a double-armed lever 25, which is provided at one end with an operating contact 26 adapted to make with a contact 27 xed on the plate 1. The end in question of the lever 25 is biased by means of a tension spring 28 tending to turn the lever 25 in a counterclockwse direction, but such a turning movement is prevented by a pawl 29 formed on a rocking lever 35, which in the position shown in Fig. 3 engages with lever 25 under the action of a tension spring 33 via a pin 30 connected with the lever 25. The lever 25 also carries an arm 31 provided with a pin 32 cooperating with a bell crank lever 34 which, like the lever 35 carrying the pawl 29, is pivotable round an axle 36.

A tension spring 37 acts on the lever 34, tending to hold it in the position shown.

When an operating current acts on the moving coil 5 via the leads 7 and 8, the double-armed lever 17 is released in the manner described with respect to Figs. l and 2. If then through the magnetic attraction, one ofY the small plates 17a or 17b strikeson the pole pieces and 11, the lever 35 carrying the pawl 29, and with its end a projecting from the air gap 12, is turned in the counter-clockwise direction, so that the pawl 29 releases the pin 30. Thus the lever 25, by the action of the tension spring 28, is able to turn in the counterclockwise direction, so that the operating contacts 25 and 27 .are closed with considerable pressure.

In order to restore the relay 2 into its starting position, a press button 21 is provided, with the aid of which the lever 25 can be turned in the clockwise direction until the pawl 29 again engages at the back of the pin 30. Simultaneously the pin 32 urges the bell crank lever 34 in a clock-wise direction. The lower part of the lever 34 is forked, and the ends of this fork emerge from the air gap 12 to bring the double-armed lever 17 once more into the position of unstable equilibrium shown, in a similar way to that described'for the actuation of the fork 23 in connection with the embodiment of Figs. l and 2. The indicator 6 thereby engages in the recess 20. After release of the button 21, the lever 34 moves back into the starting position shown, under the action of the spring 37. It will be immediately apparent that the operating circuit in the case of both embodiments of the invention is kept automatically closed until the actuation of the press button 21, either through the attraction of the permanent magnet 9 or through the spring 28.

Although the invention has been illustrated and described with reference to preferred embodiments thereof, it will be clear to those skilled in the art that it is in no way limited to the details of such embodiments or to the specic examples described, but is capable of numerous modifications within the scope of the appended claims.

I claim:

l. In an electric relay having a pointer, adapted to perform small oscillations in a predetermined plane, a two-armed lever arranged for pivotal motion about an axis arranged substantially at right angles to said predetermined plane of said small oscillations performed by saidV pointer, means being rigid with said two-armed lever and engaging the tip of said pointer in the normal position thereof, in combination, a pair of plates consisting of ferromagnetic material, said plates being attached, respectively, to the ends of said two-armed lever, permanent magnetic means cooperating with said pair of ferromagnetic plates whereby in normal position said ferromagnetic plates are under equal magnetic forces, and manually operable means for returning said ferromagnetic plates into the normal position thereof.

2. In a relay as claimed in claiml, said manually operable means 'being designed as a press button, and resilient means urging said press button into one end position thereof.

3. In a relay as claimed in claim 2, said permanent magnetic means being designed as pole pieces having ends separated from each other by a gap, and a forkshaped member attached to said press button for returning upon an operation of the same said ferromagnetic plates into the normal position thereof.

4. In a relay as claimed in claim 1, a second twoarmed lever being connected with said manually operable means, a rocking lever rocking about a stationary pivot and being maintained in one end position thereof by a first pin attached to one arm of said second twoarmed lever, a bell crank lever arranged for rotation about said pivot of said'rocking lever, a second pin arranged on a projecting arm of said rocking lever and cooperating with an` arm of said bell crank lever, and resilient means urging said rocking leverA and said bell crank lever into the initial position thereof in which said rocking lever engages said rst pin of said second twoarmed lever and said arm of said bell crank lever engages said second pin arranged on said projecting arm of said rocking lever.

5. In a relay as claimed in claim-4rst contact means arranged at one end ofsaid second two-armed lever, and stationary contact means adapted for cooperation with said rst contact means, and resilient means urging said first contact means into a position making contact with said stationary contact means when said rocking lever disengages said rst pink of said second two-armed lever.

6. In a relay as claimed in claim 3, and an electrical terminal attached to each of said pole pieces, said pole pieces being electrically conductive and insulated from each other, and said plates of ferro-magnetic material being adapted to electrically interconnect said pole pieces when said gap is bridged by one of said plates.

7. In a relay as claimed in claim 4, and a magnet connected with said pole pieces, said magnet consisting of an electrically non-conductor oxide material and having a bore for penetration by the shaft of the press button.

vReferences Cited in the file of this' patent UNITEDSTATES PATENTS 510,003 Deieny Dee. 5, 1893 787,318 wane Apr. 11, 1905 814,501 Auen Mee. 6, 1906 1,004,420 neegn sept. 26, 1911 2,014,385 Lamb sept. 17, 1935 2,262,504 Lamb Nov. 1'1, 1.941

2,380,851 Lamb July 31, 1945 FOREIGN PATENTS 560,917 Great Britain Apr. 26, 1944 

